1. Field of the Invention
The present invention relates to climbers which grasp upright columnar members such as trees, poles or the like, and more particularly, to stands formed of two climbing members which are alternately raised by the user to attain a desired elevation in a tree, or on a pole or the like. The present invention permits automatic or self-adjustment of the spacing of the grasping members so as to readily effect adjustment of the angle of each climber relative to the upright columnar member.
2. Description of the Prior Art
A two-part grasping-type tree climbing stand is disclosed in U.S. Pat. No. 4,331,216 to the present inventor, the teachings of which are hereby incorporated by reference. Such patent does not, however, provide for automatic or self-adjustment of the grasping members so that optimum angles of the climbers relative to the upright columnar member can be maintained throughout the ascent and/or descent.
A tree trunk is tapered and has a reduced diameter as elevation along the trunk is increased. To account for this, in conventional two-part climbing stands, it is important to set the initial spacing of the gripping portions of the tree climbing apparatus so as to initially engage both upper and lower frames with the outwardly extending ends oriented at a sufficient upward angle relative to the columnar member such that as the two parts are moved upward in step-wise or tandem alternating fashion, the angle attained at the desired elevation will result in the seat and footrest being substantially level or parallel to the ground. Alternatively, it may be desirable to have either or both frames oriented at a slight angle with the outward end cocked upward relative to the columnar member such that the user will tend to move or fall toward the columnar member rather than away from it.
Tree climbing apparatus typically are used by hunters. The hunting environment is frequently characterized by climbing trees in dark, wet and cold conditions, in situations in which minimizing noise is desirable. Initial ascent of a tree is often accompanied by a feeling of excitement and anticipation. Similarly, descent of a tree after a "kill" can be under excited conditions. Alternatively, after a long day of waiting in the cold and wet, a tired, exasperated and hungry hunter must descend the tree. Human nature being what it is, if the initial angle is not chosen properly, and the angle at the desired elevation is thus tilted downward, users frequently tend not to lower the tree stand, reestablish a better starting angle, and start over. Hence, less than optimum angles frequently result with attendant hazards to the users.
It is therefore desirable to be able to adjust the angle as the two parts are advanced up the tree.
Several U.S. patents show attempts which have been made to provide adjustable tree stand climbing members:
U.S. Pat. No. 4,997,063 to Bradley discloses a tree stand wherein the length of suspension braces 28, 29, 53 and 54 can be changed by turning turn buckles 36 so as to vary the angle of pivotable platforms 22 and 52.
U.S. Pat. No. 4,995,475 to Berkbuegler discloses a tree stand which is similar in concept to the Bradley device wherein the support arms 24 have rotatable adjustment sleeves 25, threaded at both of its ends, which, when turned, lengthens the support arms thereby adjusting the angle of the platform.
U.S. Pat. No. 4,428,459 to Peck and U.S. Pat. No. 4,834,217 to Manes disclose a tree stand having spring bias locking pins.
In addition, in order to tether or connect upper and lower platforms, U.S. Pat. No. 4,549,633 to Merritt U.S. Pat. No. 4,321,983 to Nelson and U.S. Pat. No. 3,485,320 to Jones disclose tree strands having cords or straps connecting the upper and lower platforms.
However, none of these prior art tree climbers permit ready automatic or self-adjustment of the gripping or grasping members such that the optimum desired platform angle can be readily adjusted and maintained, especially taking into account the conditions under which such tree climbers are typically used.